No I can not recommend doing this. If you have limited computer DIY skill you could trash your machine.
This is a very advanced DIY project with much more than just 6 steps. For example the CPU upgrade has 3 steps to access the CPU - it glossed over the 9 steps to get to the processor.
You have to purchase a used CPU that Apple used on this build (you can't just drop in any i7 or there will be EFI and OS conflicts) your actual speed increase for most tasks will hardly be noticeable.
You will have a custom box that you will be stuck with until it dies (no one will pay you anywhere near what you put into this custom build should you want to sell it). That's why you don't see much about it online. For some talented people it's a cheap way into an i7 iMac... but for most others it's a potential money trap.
So, if you are an experienced Machead that wants a custom build and the fact you have such a machine is your raison d'etre go for it. But if this is your first DIY project I stick to upgrading the HD.